Hepatitis delta virus which causes severe acute and chronic liver disease was discovered following the detection of a novel antigen-antibody system in hepatitis B virus carriers. Currently, HDV is classified as a subviral satellite of hepatitis B virus. However, unlike other satellite viruses, the dependence of HDV on HBV is limited solely to the provision of an envelope of hepatitis B surface antigen for virus assembly.  Research into the molecular virology of the HDV life cycle has revealed a fascinating collection of biology. These insights are now beginning to be translated into new potential treatment strategies. There are currently still an estimated 15 million HDV carriers worldwide.   .